g4 impact of climate change, food demands and trans-boundary agreement on water resources in the...
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by Bharat Sharma, U. Amarasinghe, M. Lal, and P. Saikia Presented at the GBDC Reflection Workshop, November 2013TRANSCRIPT
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Water for a food-secure world
Bharat Sharma, U. Amarasinghe, M. Lal, and P. Saikia International Water Management Institute
Ganges Basin Development Challenge Reflection Workshop of the CPWFSarina Hotel, Dhaka, Bangladesh;
November 12-13, 2013
Impact of Climate Change, Food Demands and Trans-boundary Agreement on Water
Resources in the Ganges Basin in Bangladesh(G4 Project)
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Annual Water Balance Components – Ganges ( 1981- 2010)
19811982
19831984
19851986
19871988
19891990
19911992
19931994
19951996
19971998
19992000
20012002
20032004
20052006
20072008
20092010
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Precipitation ETa Water yield
Year
mm
Rainfall - 609 to 1796 mm/y Water yield - 250 to 1300 mm/y
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Climate Change Scenario
CC data :
Climate data from the GCM, Hadley Centre Coupled Model, version 3 (HadCM3) was downscaled with PRECIS for the GRB under A1B Special Report on Emission Scenarios (SRES) scenarios.
Future projection years : 2030, 2050
To represent the hydrological variables in 2030, the average values between 2025 and 2035 were taken. The average values of the hydrological variables between 2045 and 2055 were used to represent the values in the year 2050.
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Areas with increased and reduced precipitation in 2030 and 2050 compared to the baseline
In 2030, precipitation will be reduced over 47% of the basin area compared to the baseline period and this value will be 36% in 2050
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Spatial Distribution of Precipitation, Water yield, ETa and Snow melt ( baseline)
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Spatial Distribution of Precipitation, Water Yield, ETa and Snow Melt ( 2030)
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Water for a food-secure world
Spatial Distribution of Precipitation, Water Yield, ETa and Snow Melt ( 2050)
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Water for a food-secure world
Implications of the Analysis:
In the A1B scenario considered in this study, precipitation is projected to increase.
This would lead to higher PET and increased ETa in 2030 and 2050 compared to the baseline period.
For agriculture sector, this could mean a higher demand for irrigation water. In future, the average water yield over the GRB will increase by about 172 mm and the average shallow aquifer recharge will increase by about 27 mm in 2050 compared to the baseline period.
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Water for a food-secure world
This is attributed to the higher precipitation in some parts of the basin, especially during wet season.
A1B climate change scenario will have positive effect in terms of the water availability in the GRB. But with a lot of spatial and temporal variability within the basin. This implies increase in extreme events in the basin.
A holistic approach of developing infrastructure to capture the increased flow in the river, and enhanced groundwater recharge techniques should be a priority in the GRB. This will help in mitigating adverse effects of climate change in the future.
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Water for a food-secure world04/13/2023 10
2. Water for Food in Bangladesh: Outlook to 2030
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Composition of daily calorie supply per person in Bangladesh
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Actual and forecasts of GDP and calorie supply from various cereal, animal and other crop products
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Change in cropping and irrigation patterns in Bangladesh
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Auto Regressive Integrated Moving Average (ARIMA ) models predict:
• Further decline in Aus rice area—to 0.7 Mha by 2020, and 0.2 Mha by 2030,
• No significant changes in Aman rice area. It shall stabilize between 5.7 to 6.1 Mha, and
• Further increase in Boro rice area-- to 5.7 Mha by 2020 and another 1 Mha by 2030. The predicted increase in Boro rice area will be significantly more than the decline in Aus rice area
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Area and yield of Aus, Aman and Boro rice in Bangladesh
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The ARIMA models predict:
Aus rice yield to increase 2.0% annually between 2010 and
2020; 1.2% annually in the 2020’s; and to reach 2.4 t/ha by
2030.
Aman rice yield to increase 1.8 and 1.1% annually in the next
two decades, and reach 2.8 t/ha by 2030; and
Boro rice yield to increase 1.2 and 1.0% annually in the next
two decades, and reach 4.8 t/ha by 2030.
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Variation of yield and WP with total CWU across 23 districts
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Time Season Area (Mha)
CWU (Bm3)
Total production (Mt)
Water productivity(Kg/m3)
Savings of irrigation CWU (Bm3) by only meeting the rice demand1
Total Irrigated Total Irrigation WP growth scenarios2
0% 5% 10%
2010 Aus 1.1 0.0 4.8 0.0 1.9 0.40 - - -
Aman 5.6 0.6 30.7 0.0 12.5 0.41 - - -
Boro 4.7 4.5 27.5 16.5 18.3 0.67 - - -
Total 11.4 5.1 63.0 16.5 32.8 0.52 - - -
2020 Aus 0.7 0.0 3.2 0.0 1.5 0.47 - - -
Aman 5.7 0.0 30.8 0.0 14.1 0.46 - - -
Boro 5.7 5.7 33.9 20.9 24.6 0.73 2.60 2.74 2.89
Total 12.1 5.7 67.9 20.9 40.2 0.59 - - -
2030 Aus 0.2 0.0 1.1 0.0 0.6 0.53 - - -
Aman 5.7 0.0 30.8 0.0 15.9 0.52 - - -
Boro 6.7 6.7 39.9 24.5 32.1 0.81 6.08 6.40 6.76
Total 12.6 6.7 71.7 24.5 48.6 0.68 - - -
Implications for Water Demand upto 2030
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3. Indo-Bangladesh trans-boundary river basin cooperation :
A Policy Analysis
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• Identify the current challenges in Indo-Bangladesh Ganges River water sharing and management.
• Review the negotiation history and implementation of the 30-years Indo-Bangladesh Ganges water sharing treaty signed in 1996.
• To explore and recommend avenues for cooperation over Ganges not just for water sharing but also a basin-wide development approach.
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Source: (Salman and Uprety, 2002).
The 1996 Ganges Water Sharing Treaty The 1996 treaty provided the provisions for water sharing of Ganges at the
Farakka border during dry seasons, operational between January 1 and May 31 each year. Under the treaty an arrangement/water sharing formula was reached between the two countries on the amount of water transferred from Farakka into the Padma during the lean season.
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Water available at Farakka
Share of India Share of Bangladesh
70,000 cusec or less
50% 50%
70,000-75,000 cusec
Residual flow 35,000 cusec
Greater than 75,000 cusec
40,000 cusec Residual flow
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Study Findings Inadequate implementation of the 1996 Ganges Water
Treaty. The 1996 water arrangement is based on the average flow observed (1949-73)
which is 12105.4 cumecs and the annual discharge is 382 BCM. There have been considerable changes and variation in the flow of water at Farakka after 1996.
Morphological Changes of the Ganges River system has been noticed which will pose serious threats to the 1996 water sharing arrangement.
The rapid change in the Ganges system and the decrease in the dry season freshwater flow at Farakka barrage is creating a stress in the Indo-Bangladesh cooperation.
Changing course of the Ganges and the threat of the river outflowing the Farakka Barrage.
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Similar concerns noticed in both India and Bangladesh over the low dry season freshwater flow in the Ganges:
the Bhagirathi-Hooghly river system in West Bengal and Gorai river system in Bangladesh.
Gorai remains dry during lean season. Demographic changes in the GDA of West Bengal and Bangladesh has been
noticed. Increasing usages of water in the upstream is also affecting the flow of freshwater
at the Farakka point. Increasing siltation and changing course of the river channel has also resulted in
erosion of vast tracts of land around Farakka. River bed erosion along the Bhagirathi-Hooghly River in West Bengal and
Ganges/Padma in Bangladesh is noticed. Reduced freshwater flow also resulting in accumulation of sedimentation. Small Rivers and Distributaries along the Lower Ganges Basin is getting dried and
disconnected from the main rivers.
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Source: World Bank
Map showing the Gorai River
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Map Showing the Farakka Barrage and Feeder Canal Map Showing the Feeder canal and Bhagirathi river
Source: Kolkata Port Trust04/13/2023 24
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The increasing sedimentation, loose texture of the soil and the varying discharge from the Farakka barrage into the Bhagirathi has led to a meander bend of the river channel.
Shankhapur-Moyapur cut-off
Source: Hydraulic Department, Kolkata Port Trust
Bishnupur-Charchakundi cut-off
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The reduced freshwater flow along the Bhagirathi-Hooghly River causing major threats for the navigability of the Kolkata port.
The minimum flow of 40,000 cusec, required for the navigability of the Kolkata port has not been met( as mentioned by authorities of Kolkata Port Trust)
Analysis shows that the most benefited area from the water diverted from the barrage is the feeder canal area.
Navigational routes in Bangladesh(mostly the distributaries of Ganges) suffers from low flow of Ganges during dry season causing serious threat to its inland waterways.
The low flow of freshwater has resulted in accumulation of sediments on river bed which has reduced the depth required for navigation of bigger vessels and ships. The country mostly dependent on its inland waterways for trade and transportation is under serious threat.
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Joint River Commission(JRC) must be strengthened
• Joint projects and research studies should be conducted under a joint team consisting of technical and policy experts from both the riparian states.
Basin Commissions must be set up in each of the riparian countries supervised by JRC.
• Meet an agreement towards the augmentation of flow during lean season.
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THANK YOU
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